After news media reports suggested that the man who carried out the massacre at a gay nightclub here may have himself been gay, the company that bills itself as “the world’s largest gay hookup site” put out what amounted to a distress call, asking members who may have been in contact with the gunman, Omar Mateen, to come forward.

In an attempt to find an account connected to the killer, the site, Adam4Adam combed through the profile photos of every one of its 300,000 Florida members and researched 20 email addresses used by Mr. Mateen over the years that the company said had been provided by the F.B.I.

Adam4Adam came up with nothing.

“I think it was a hoax,” David Lesage, a spokesman for the Montreal-based company, said about the reports that Mr. Mateen had used Adam4Adam and other dating sites and apps for gay men.